DLR (Dynamic Line Rating)

DLR is part of the OTLM Center application. Our model is based on a modified CIGRE mathematical model that combines real-time measured conductor temperature, load and ambient conditions along the OHL line. Combining all the measurements within a CIGRE mathematical model enables accurate information of the maximum current that conductor can carry – ampacity.  Ampacity prediction is based on the cooperation with several weather prediction providers.

The transmission capacity (Ampacity) of OHL is determined by two key factors. The first is the maximum permanently permitted conductor temperature which is set at 80 °C for ACSR. The second is minimal allowed safety clearance from the conductor to the ground or object beneath which is defined by the safety standards and depends on the type of object and voltage level of the OHL. The first factor affects the plastic deformation of the conductor which is why, after a certain number of thermal cycles, it can lead to the rupture or slippage of the conductor from terminal clamps. The second factor has a considerable influence on the safety of the people and the environment from voltage flashovers.

Both factors can be affected by a number of physical quantities which can change instantly. Solar radiation, air temperature, speed and wind direction have a direct impact on the heating and cooling of the conductor. Considering that these physical quantities are very difficult to predict or even estimate, the methods for determining the maximum allowable transmission capacity of the OHL are very conservative.

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